Movable flame holder for combustion apparatus



R. T. FRENCH EI'AL Jul-y 30, 1957 2,800,765

' MovABLE FLAME HOLDER FOR coMBUsTroN APPARATUS filed Aug. 27, 1947 2Shee'ts-Sheet 1 INVEN RALPH T F' RsNcH,

TORS

WALTER D.PoucHoT.

ATTORNEY I\l I l l l I vm... um Nv @n July 30, 1957 R. T. FRENCH ETAL2,800,765

MOVABLE FLAME HOLDER FOR COMBUSTION APPARATUS Filed Aug. 27,- 194'? 2Sheets-Sheet 2 1 .f INVENToRs RALPH TZ FRENCH 1TH l O n D n m T A mmUnited States Patent O MDVABLE FLAME HOLDER FOR COMBUSTION APPARATUSRalph T. French, Havertown, and Walter D. Pouchot,

Moylan, Pa., assignors to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Penn- Sylvania Application August 27,1947, Serial No. 770,800

1 Claim. (Cl. 60-35.6)

This invention relates to combustion apparatus, more particularly toflame holders therefor, and has for an obj-ect to provide improvedapparatus of this character.

In combustion apparatus where the gases to support combustion flowthrough the combustion chamber at velocities in excess of fifty Vfeetper second, it is likely to be difficult to maintain a suitable flameformation. In some cases the ilarne may be entirely extinguished and inother cases it may be forced a considerable distance downstream of thelocation where burning is desired.

To avoid these and other dculties resulting from high velocities ofgases through combustion chambers, it has heretofore been proposed toprovide, in the cornbustion chamber and at a point upstream of thedesired flame location, a llame holder. Such arne holder usually extendsgenerally transversely of the stream of gases and serves to produce inthe stream a degree of stagnancy sucient to permit retention of theflame at the desired location.

Such flame holders, while performing a very necessary function, havecertain disadvantages, not the least of which is that they seriouslyobstruct the normal flow path through the combustion chambers, and mayreduce the effective cross sectional area thereof as much as 43 percent.

One of the most common uses of flame holders is in tail burners or afterburners for aviation gas turbine power plants, where the exhaust gasesfrom the turbine are reheated before passing through an exhaust nozzleas an aircraft-propelling jet. Such tail burners customarily are usedonly a small portion of the total operating time of the gas turbinepower plant, as, for example, when rapid climbs or short Vbursts ofexcess speed are desired. The remainder of the time, when the tailburner is not in operation, maximum efficiency of the power plantisseriously impaired, due to the excessive pressure drop resulting fromreduction in effective ow area by the llame holder.

The present invention substantially eliminates this primary drawback ofexisting flame holders by so constructing and mounting the same thatwhen the tail burner or other combustion apparatus with which the llameholder is associated is not in use the flame holder can be moved by thepilot to a position where its obstructing effect is substantiallyeliminated or at least materially reduced.

Accordingly, another object of the invention is to provide a flameholder which is adjustable between an operative position when itproduces a degree of stagnancy accompanied by a material pressure dropand an inoperative position where the pressure drop `is materiallyreduced.

Yet another object of the .invention is to :mount a ame holder forpivotal movement between operative and inoperative positions.

Patented July 30, 1957 A further object of the invention is to provide,in a gas turbine power plant having an exhaust nozzle and a tail burnerbetween the turbine and said nozzle, means for throttling the nozzlewhen the tail burner is inoperative and a llame holder adjustablebetween operative and inoperative positions, together with mechanism forsimultaneously moving the nozzle throttling means to operative positionand the arne holder to inoperative position, and vice versa.

These and other objects are effected by the invention as will beapparent from the following description and claim taken in connectionwith the accompanying drawings, forming a part of this application, inwhich:

Figs. la and 1b, taken together, constitute a longitudinal sectionalview through an aviation gas turbine power plant constructed inaccordance with the present invention;

Fig. 2 is a sectional view, taken along the line ll-il of Fig. 3,looking in the direction indicated by the arrows;

Fig. 3 is 'a fragmentary side elevational view of a portion of thestructure shown in Fig. lb;

Fig. 4 is a View similar to Fig. lb, but showing a modified llameholder;

Fig. 5 is a sectional view, taken along the line V--V of Fig. 4, lookingin the direction indicated by the arrows;

Fig. 6 is a sectional view, taken along the line VI-VI of Fig. 5,looking in the direction indicated by the arrows; and

Fig. 7 is a sectional view, taken along the line Vll-VII of Fig. 5,looking in the direction indicated by the arrows.

As previously indicated, the present invention, while not limitedthereto, is particularly adapted for use with a gas turbine power plantof the type employed on aircraft to drive the propeller or an electricgenerator and/or to supply motive fluid for jet propulsion of theaircraft. Such a plant preferably comprises a streamlined tubular casinghaving mounted axially therein a compressor adjacent the forward orinlet end, a turbine in the rearward hall:` of the power plant, andcombustion apparatus located between the compressor and the turbine forheating the compressed air and which discharges the hot gases atsuitable temperature and pressure to the turbine. The gases on leavingthe turbine are discharged through a nozzle provided at the rear of theVcasing and may aid in propelling the aircraft.

Referring now to the drawings more in detail, the power plant shown inFigs. la and 1b and indicated in its entirety by the reference character10, is adapted to be mounted in or 4on the fuselage or wing of anaircraft with the left end or intake 11, as viewed in Fig. la, pointedin the direction of flight.

The plant comprises an outer shell or casing structure 12-12a providingan annular air duct or passage 13 extending fore and aft with respect tothe aircraft. This casing has mounted therein, along its longitudinalaxis, a fairing cone 14 adapted to house gearing connecting through ahollow guide vane 16 with auxiliaries (not shown), an axial flowcompressor 17, combustion apparatus generally indicated 18, a turbine 19which drives the compressor, and a nozzle 21 defined by the rear end ofthe casing 12a. Additionally, the passage 13 provides a tail burnercombustion space 22 between the turbine 19 and the exhaust nozzle 21,and in which combustion space is positioned the llame holder 23constituting the primary element of the present invention.

Air enters .at the intake 11 and flows substantially straight throughthe plant, passing .through the compres- 3 sor 17 where its pressure israised, and into the combustion apparatus 18 where it is heated. The hotgases, comprising the products of combustion and excess air heated bythe combustion, on leaving the combustion apparatus are directed bysuitable guide vanes or nozzles 24 against the blades 25 of the turbinediscs 26 and then are discharged throughithe nozzle 21 to propel theaircraft.

By reference to Fig. la it will be seen that the compressor and turbinerotors are interconnected by means of a shaft 27 supported by suitablebearings 28 and enclosed by an inner wall structure, generally indicated29, which protects the shaft and bearings from high temperatures andalso defines a portion of the annular air flow passage 13 in which thecombustion apparatus 18 is located.

The combustion apparatus comprises annular walls 31, 32, 33 and 34, thewalls 31 and 32 being joined at their upstream ends by an end wall 35and the walls 33 and 34 similarly being joined at their upstream ends bythe wall 36. The walls 32 `and 33 are joined at their downstream ends,as at 37, whereby there are provided annular burner spaces -38 and 39overlapped by annular air spaces 40, 41 and 42. Fuel is supplied to theburner spaces 38 and 39 by annular series of nozzles (not shown) carriedby the end walls 35 and 36.

Referring now to Fig. lb for a description of the tail burner, it willbe seen that a fairing cone 45, positioned with its base in closeproximity to the downstream end of the turbine 19, provides for gradualdivergence of the annular passage 13 from the turbine outlet to thepoint of the fairing cone, where the passage becomes cylindrical incross section. Preferably, the fairing cone is supported by a pluralityof radial struts 46, one of which is hollow and houses fuel supplyconduits 47, 48 and 49. terminating in annular fuel manifolds 51, 52 and53, respectively. The manifolds 51 and 52 have circumferentially-spacedfuel emission openings for directing sprays of fuel upstream, While themanifold 53 has similar openings for directing fuel sprays downstream.

The llame holder 23 is disposed within the tail burner combustion space22 at a point slightly downstream of the fairing cone 45 and serves toproduce in the stream of gases flowing therepast a degree of stagnancysuflicient to maintain a llame formation in the combustion space 22slightly downstream of the llame holder.

The particular shape of the baille or shield elements making up theflame holder is not critical to the present invention, but has beenillustrated as Vhaving the f orm of a hollow cone 55 pointed upstream,and each such cone is connected to adjacent cones by bridge members 56which are concave at their downstream .sides vto promote spreading ofthe llame transversely of the combustion space, from cone to cone.

As best shown in Fig. 2, the llame holder 23 is divided'- into twoseparate semi-circular halves, each such half` being mounted on a shaft60, journaled in bearings 61- carried by the casing walls 12-12a. One ofthe shafts is adapted to be oscillated through an angle of 90 4degreesby means of the arm 62 secured thereon at one end, and whose other endis connected to a longitudinallyreciprocable rod 63, operable at thewill of the pilot.

That end of the arm 62 which is secured to its Vshaft 60 is providedwith a gear segment 60a meshing with a.

corresponding gear segment 60h secured to the other y shaft 60, wherebyrotation of the first` shaft 60 produces 4 The flame holder movesbetween an operative position where it extends generally transversely ofthe tail burner combustion chamber, as shown in full lines (Fig. 4) andan inoperative position where it extends axially of the combustionchamber, parallel to the direction of flow of turbine exhaust gasestherethrough and shown in dotdash lines.

After the llame holder (either form) has been moved to operativeposition and fuel supplied to the gas stream through one or more of thefuel manifolds 51, 52 or 53 upstream thereof, the fuel must be ignited,preferably at a relatively sheltered point in the gas stream, and tothis end ignition means, such as the spark plug 75, is positioned at thedownstream side of one of the inverted f cones 55 (Figs. 5 and 6) withits cable 76 passing through a bore 77 in the shaft 71. While notillustrated, it will be obvious that a ysimilar ignition means would beprovided with a llame holder such as shown in Figs. 1 to 3.

Inasmuch as a far larger volume of heated gases exhaust through thenozzle 21 when the tail burner is in operation than when it isinoperative, it is desirable'to be able to enlarge the nozzle, and thisis accomplished by the adjustable sections 80 and 81, pivoted at 82 andmovable between the full line and dot-dash line positions indicated inFig. 4.

The details ofthis nozzle adjusting means form no part of the presentinvention, being separately disclosed and claimed in copendingapplication by Carl F. Koenig III, Robert E. Weiler and James D. Brown,Serial No. 770,836, filed August 27, 1947, now abandoned, abstractpublished November l, 1949 in 628 O. G. 256, and as-v signed to theassignee of the present application. However, the present invention doesinclude the novel cooperation between the llame holder and theadjustable nozzle, for when the tail burner is to be used the nozzleusually would be opened and the flame holder moved to operativeposition, and when the tail burner is out of use the nozzle usuallywould be closed and the flame holder moved to inoperative position. Tothis end, a rod extends from the arm 72 to the arm 86 on the nozzlepivot 82, so that the flame holder and nozzle sections lare movedsimultaneously and by a single operation of the pilot.

It will be apparent that a similar interconnecting operating mechanismfor the flame holder and nozzle could I be provided for flame holdingapparatus such as shown opposite rotation of the other shaft, with theresult that i in Fig. la, but a showing thereof has been omitted for thesake of clearness of disclosure.

While the invention has been shown in several forms, it will be obviousto those skilled in the art that it is not so limited, but issusceptible of various other changes and modifications without departingfrom the spirit thereof.

What is claimed is:

Inl a .power plant, `structure defining a combustion chamber having aninlet and an outlet and adapted for ilow of gases therethrough atvelocities exceeding 50 feet per second, a llame-holder for effecting adegree of stagnancy in the stream of gases flowing through the chambersuch that a llame formation may be maintained within the chamber, meanssupporting the llame-holder for movement between an operative positionwhere it produces a material pressure drop in the gas stream and aninoperative position where the pressure drop produced thereby ismaterially reduced, adjustable means. -associated with the outlet of thecombustion chamberl and movable between an operative position where itthrottles the gas stream leaving the combustion chamber and inoperativeposition where its throttling action isv materially reduced, and meansfor moving the llame holder to operative position upon movement of thethrot- I tling means to inoperative position and for moving the llameholder to inoperative position upon movement of the throttling means tooperative position.

(References on following-page) i' References Cited in the le of thispatent 2,346,815 2,409,176 UNITED STATES PATENTS 526,122 1,336,261 ScottApr. 6, 1920 2,707,372 1,524,294 Fogler June 16, 1925 5 2,181,261 BreeseNov. 28, 1939 2,296,023 Dallenbach et al. Sept. 15, 1942 6 Breese Apr.18, 1944 Allen Oct. 15, 1946 Darlington Oct. 17, 1950 Cleveland May 3,1955 OTHER REFERENCES S. A. E. Journal, September 1946, pages 507-508.

